Well treating apparatus and method



Feb. 5,: 1963 E. N. JONES WELL TREATING APPARATUS AND METHOD 2 Sheets-Sheet 1 Filed Oct. 2. 1959 Feb. 5,-i 1963 E. N. JONES WELL TREATING APPARATUS AND METHOD Filed Oct. 2, 1959 2 Sheets-Sheet 2 NBbnnEF United States Patent O 3,076,503 WELL TREATING APPARATUS AND METHOD Edward N. Jones, P.0. Box 107, Pettus, Tex. Filed Oct. 2, 1959, Ser. No. 844,138 21 Claims. (Cl. 166-1) This invention relates to -a well treating apparatus and method, and more specifically to an apparatus which. may be lowered into a well tubing to coat the internal wall of the tubing in situ, with a corrosion inhibitor, and to a method of coating the internal wall of the tubing, in situ.

In using well tubing, especially tubing 4used in oil wells, it frequently becomes necessary to apply a coating on the inner wall thereof. This coating may be a corrosion inhibitor which protects the metal well tubing against attack from the corrosive substances found in cert-ain oil, or a sealing compound to seal points in a string of tubing where leaks may exist.

Previous practice involved the coating of the interior of the tubing on the surface and then lowering the string of piping into the well bore. It has .been lfound that various Ioperations used in connection with lowering of the .string of piping into the well bore, such as bending, truckmg, etc., produce minute cracks in the protective coating, which Iare not readily perceptible. Localized pitting occurs at these minute cracks, frequently causing undesirable leaks and requiring the replacement of the tubing.

It is an object of .the invention to provide a novel well treating apparatus which can be lowered into a string of well tubing, in situ, to apply a corrosion inhibitor coating on the interior wall of the tubing.

It is a further object of the invention to provide a novel well treating apparatus which can be lowered into a string of well tubing, in situ, containing oil, to apply a corrosion inhibitor coating on the interior Wall of the tubing, in which the oil, gas, or other uids in the tub-ing can pass through the apparatus when it is lowered or raised in the Itubing.

Itis a further object of the invention to provide a novel well treating apparatus for lowering into a well tubing, in situ, to apply a corrosion inhibitor coating on the interior wall of the tubing, in which the force of gravity is employed for lowering Ithe treating apparatus.

It is a further object of the invention to provide a novel well treating apparatus for lowering into a well tubing, in situ, to apply a predetermined quantity of corrosion inhibitor coating, including replaceable parts to accommodate dilerent predetermined quantities of inhibitor.

It is a further object of the invention to provide a novel arrangement for charging a well treating apparatus intended to be lowered into a lwell tubing, in situ, to apply a corrosion inhibitor on the interior wall of the tubing.

It is a further object of the invention to provide a novel well treating apparatus for a producing oil well adapted to carry a charge of treating liquid to apply a coating on the interior wall of a well tubing, in situ, as the apparatus is lowered, in which excess liquid can be dumped at the bottom of the string of tubing to form a reservoir of coating liquid which may be carried up by the oil in the well to further coat the tubing.

It is a further object of the invention to provide a novel well treating apparatus adapted to carry a charge of treating liquid to apply a coating on the interior of a string of well tubing in-situ as the lapparatus is lowered therein, in which the apparatus includes structure, cooperable with the string of tubing, permitting the dumping of any unused portion of liquid at any joint in the string of tubing, or at the bottom of the string of tubing.

Itis a still further object of the invention to provide a ice novel method of coating a string of well tubing in a producing oil well, in situ, by passing a coating apparatus therethrough to apply a protective coating thereon and 1n dumping excess material at the bottom of the tubing to be carried up by the oil in the well to form a further coating on the well tubing.

Other and further objects of the invention wil be apparent from the following description taken in conjunction with the accompanying drawing in which:

FIG. l is a view, partially in section, of the upper end of a well tubing, showing one form of a novel well treating apparatus in charging position in the lubricating housiFIG. 2 is an enlarged sectional view of the novel well treating apparatus of FIG. l within the well tubing;

FIG. 3 is a sectional view through the upper end of the well treating apparatus taken on the line 3 3 of FIG. 2;

FIG. 4 is a sectional View through the well tubing looking toward the lower end of the well treating apparatus, taken on the line 4 4 of FIG. 2;

FIG. 5 is a sectional view of the lower end of a modified form of well treating apparatus employing a novel dumping valve, showing the valve in closed position;

FIG. 6 is a transverse sectional view on the line 6 6 of FIG. 5;

FIG. 7 is a sectional View, similar to FIG. 5, showing the apparatus in its dumping positions; land FIG. 8 is an enlarged detail view illustrating `a latch and tripping mechanism.

Referring to FIG. l of the accompanying drawing, the numeral 10 designates a string of well tubing surrounded by the usual casing or protector string 12, representing the conventional practice in producing oil wells. The upper end of the well tubing 10 is connected with the conventional Christmas tree 14, having branch lines 16 controlled by individual gate valves 18. A master gate valve 20 is provided to control the flow through the upper end of the Well tubing.

A lubricator 22 is secured to the upper end of the Christmas tree 14, as by being threaded therein. The lubricator 22 has the same internal diameter as the Well tubing 10 and is arranged coaxially therewith. The upper end of the lubricator is closed by a stuiiing box 24 to prevent the loss of fluid from the system. The side wall of the lubricator has a lower pipe connection 26 with a valve 28 therein, and an upper pipe connection 30 with a valve 32 therein.

`One form of well treating apparatus, forming the subject matter of this invention, is shown in FIGS. l and 2, and is designated in its entirety by the numeral 34. This apparatus comprises an elongated tubular member 3'6, preferably of cylindrical form, provided with flanges 38 spaced inwardly from the opposite ends thereof, as more clearly shown in FIG. 2. A pair of L-shaped sealing rings 40 is inserted over the lower end of the tubular member 36, and a pair of U-shaped sealing rings 42 is inserted over the upper end of the tubular member, the inner ring in each base being adapted to rest against one of the flanges 38. The rings 40 and `42. have outer axially extending flanges 41 and 43, having an outer diameter which is equal to the inner diameter of the well tubing 10, whereby the anges engage the inner surface of the well tubing to prevent the flow of gas or liquid past the sealing rings. An end cap 44, having an internally threaded sleeve extension 48, is threaded on the lower end of the tubular member 36, and retains the sealing means 40 in position against the lower flange 38 by means of a pair of spacers y45 and a flange engaging ring 47. The lower end cap 44 has a plurality of apertures 50 therein for a Patented Feb. 5, 1963 purpose to be set forth hereinafter. An upper end cap 46, having an internally threaded sleeve portion 52, is threaded over the upper end of the tubular member 36, so that the sleeve portion 52 retains the upper sealing means 42 in position against the upper flange 38 by means of a pair of T-shaped spacers 49 and a flange engaging ring 51. The spacers 49 are provided with a plurality of apertures 53 to allow the passage of Huid under pressure to force the sealing flanges 55 tightly against the tubular member 34. Upper end cap 46 is provided with a fishing head 54 and with a plurality of apertures 56 for a purpose to be set forth hereinafter.

The hollow tubular member 36 and the end closure caps 44 and 46 enclose an interior chamber 57 adapted to receive a weight or driving bar 58. The driving bar is intended to deliver a blow to the lower end cap 44 to be raised and dropped within the chamber 57 in order to force the well treating device 34 through the well tubing, and for this purpose the driving bar is shorter than the axial distance between the end caps 44 and 46 to permit axial movement of the driving bar in chamber 57. An axial bore 60 is provided in the upper end of the driving bar 58, and a transverse bore 62 crosses said axial bore. A tight fitting pin 64 is passed through the transverse bore 62, passing through a loop 66 on one end of a cable 68 within said bore '60. The cable 68 passes through an opening 70 in the upper end cap 46 and through an opening in stuffing box 24, as shown in FIG. 1. The cable extends over an upper pulley 74 supported at 72 from the stutling box and over a lower pulley 76 to a winch, not shown. Lower pulley 76 is pivotally supported on a U-shaped mounting 82, which mounting, in turn, is secured by means of a chain 78 to a bracket 80 carried by the Christmas tree 14.

It will be noted, with reference to FIG. 2, that the driving bar 58, which may be circular in cross section, has a smaller cross sectional area than chamber 57, thereby providing an annular clearance between the outer surface of driving bar 58 and the internal wall of the tubular member 36. This annular clearance, together with the apertures 50 in lower end cap 44 and the apertures 56 in the upper end cap 46, provide an uninterrupted passage for fluid flow through the well treating apparatus from one end thereof to the other end.

In operation, the well treating apparatus 34 may be held in its upper position in the lubricator 22, as shown in FIG. l, so that the upper sealing means 42 are slightly above the point of entry of pipe connection 30. The pipe connections 26 and 30 should be placed so that they can simultaneously register with the annular space formed by the upper and lower sealing means 42 and 40, tubular member 36, and the lubricator 22. In this position, the valves 28 and 32 in the connections 26 and 30, respectively, may be opened to permit the charging of the well treating apparatus with any liquid coating material or with a suitable corrosion inhibiting material such as, for example, the amines or any other generally accepted treating compound, including plastics, rosins, sodium silicates, and other compounds that will produce a lm on the internal wall of the well tubing, which material enters through the supply connection 26. Gases or other substances, which may be in the space being charged, are forced outwardly through the upper connection 30, which functions in the nature of an equalizing or bleeding line. When the well-treating apparatus is charged, valves 28 and 32 may be -closed and the well treating apparatus may be lowered into the well tubing through the open master gate valve 20. By releasing the tension on the cable 68, the force of gravity is usually sufficient to lower the well treating apparatus through the well tubing 10. `If resistance is met to prevent this downward movement, the driving bar 58 can then be raised and dropped, which will produce a sufcient driving force to overcome any resistance that may be encountered. The sealing means 40 and 42 prevent the loss of liquid between them and the intermixture of the iluid carried by the well treating apparatus with the uids in well tubing 10. A very thin film of the corrosion inhibiting material or other material is formed on the wall of tubing 10, as the device is lowered into the Well. Larger quantities are released at the joints, where the spaced ends of adjoining pipe sections form pockets, which quantities are free to flow down the interior of the tubing 10 and cling to the tubing Wall because of the affinity of the coating material with the material of the tubing wall. These sealing means may be made or rubber, leather, canvas, or other appropriate material that will permit the application of a coating of the desired thickness on the internal wall of the well tubing. As the Well treating apparatus is being lowered, the anges 41 on the lower sealing means 40 are effective to wipe the internal wall of the well tubing 10 free of any moisture or oil and replace it with a protective coating that will prevent the corrosive materials found in some oils from attacking the wall of the well tubing. When the well treating apparatus is raised, the ilanges 43 on the sealing rings perform a similar function. The use of a pair of sealing means functions in the nature of labyrinthine packing to prevent the mixing of the material carried by the treating apparatus with Water or other substances present within the well tubing. As the well treating apparatus is lowered or raised in the well tubing, various fluids in the well tubing, such as oil or gases, are permitted to pass from one end of the well treating apparatus to the other end through the apertures 50 and 56 in the lower and upper end caps 44 and 46 arsld by way of the clearance surrounding the driving bar 5 The Well treating apparatus is selected to have a capacity in excess of that required to coat the interior wall of the tubing 10 as the apparatus is lowered, so that there remains a considerable quantity of treating liquid in the treating apparatus when it reaches the bottom of the string of well tubing 10. By lowering the well treating apparatus to a position in which the lower sealing means 40 are below the lower end of the well tubing 10, as shown in phantom lines in FIG. 2, the excess quantity of well treating liquid remaining in the well treating apparatus can be dumped into the bottom of the well, which, in this case, may be assumed to be a producing oil Well, and the well treating liquid may be assumed to be a cor rosion inhibitor having a higher ailinity for the material of the well tubing than for the oil. The corrosion inhibitor may, or may not, be miscible with the oil, but in elther event the inhibitor will be carried up with the oil 1n the pumping operation, and, because of its higher aimty for the material of the well tubing, the inhibitor will maintain a protective coating thereon. The operation above described not only contemplates the use of a coatlng apparatus to apply a coating of protective material along the entire internal wall of a tubing to protect the tubing against the corrosive effects of the oil passing therethrough, but also as a means to form a reservoir of protectlve material at the bottom of the well which may be carried up with the oil, as it is pumped, to maintain and/ or to replenish the protective coating on the interior of the well tubing, and to apply a similar protective coating along the various connecting conduits branching from the Christmas tree 14 and the various storage tanks into which they discharge.

The well treating apparatus disclosed can be modified to carry different quantities of treating material. For this purpose, tubular member 34 may be replaced by a similar tubular member 34 of greater or less axial length, and of the same diameter, which can be readily attached to the end caps 44 and 46. If necessary, a different length driving bar 58 can be substituted in such modification. It is obvious that other equivalent arrangements can be provided for permitting ilow past the driving bar 58, such as one or more axial bores extending from one end to the other of the driving bar, or by axially extending grooves on the periphery of the driving bar.

A modified form of well treating apparatus is shown in FIGS. 5, 6, 7 and 8 in which the reference numeral 84 designates the apparatus in its entirety.

The well tubing 10 is composed of a string of pipes or pipe sections 86, which are connected in end-to-end relationship by threaded couplings 88 engaging the external threaded ends of the pipe sections. The pipe sections are not in abutting relation, but are spaced slightly to form an annular groove 90 bounded by the spaced ends of the pipe sections and by the interior wall of the threaded coupling 88. Advantage is taken of these annular grooves to enable the dumping of the charge of treating liquid at various -selected points in the well tubing, as will be described hereinafter.

The well treating apparatus comprises an elongated tubular member 92 having flanges 94 spaced from the ends thereof. The upper end of the tubular member 92 is not shown in FIGS. 5 and 7, but the ange 94 thereon is spaced from the upper end the same distance as the upper flange 38 in FIG. 2, and cooperates with an end cap 46 to retain a pair of upper end sealing rings in position. The lower liange 94 is spaced farther from the end than the upper tiange. A pair of sealing rings 96 is disposed between the iianges 94 and the ends of the tubular member. These sealing rings may be of any conventional design, and are shown as having a widened base portion surrounding the tubular member 92 to assure stability and to serve as spacing means to provide a labyrinth seal. A helical spring 93 surrounds the tubular member 92, with its upper end abutting the lower flange 94 and its lower end engaging the base of the upper sealing ring 96 to urge both sealing rings against a spacer ring 100 and toward the lower end of the tubular member.

A plurality of latch members 102 are provided between the spacer ring 100 and the lower end of the tubular member 92. These latch members are generally L-shaped in configuration, and are pivotally connected for swinging movement on pivots 104 supported by spaced ears 106. The ears 106 are welded to the external wall of the tubular member 92 at spaced intervals, as shown in FIG. 6. The free ends of the latch members engage an annular groove 108 provided in the external wall of the tubular member, and are engaged by the lower surface of the spacer ring 100, which ring is urged against the free ends of the latch members 102 by the helical spring 98 acting through the sealing rings 96. The lower surface of the spacer ring is beveled at 110, as shown in FIG. 8, and the points of contact between the beveled end 110 and the free end of the latch members 102 are spaced radially inwardly of the pivots 104, so that the spring force gives rise to a radially inward component which forces the free ends of the latch members into the groove 108.

A tripping lever 114 is pivotally mounted on the pivots 104 adjacent each latch member. The tripping levers are generally triangular in configuration, as more clearly shown in FIG. 8, being pivoted Vfor swinging movement at one corner. Another corner carries a tripping pin 116 extending transversely of the plane of the lever 114 and adapted to extend between the adjacent latch member 102 and lthe tubular member 92. The third corner 118 is adapted to ride along the interior wall of the well tubing 10 when the well treating apparatus is lowered, the trip ping levers 114 tending to swing away from the tubular member 92 by force of gravity'.

A plurality of apertures 120 are provided in the tubular member 92 between the lower flange 94 and the ears 106 in a position to be covered by the base of the uppermost of the sealing rings 96, as shown in FIG. 5, which ring base constitutes a movable valve member.

In operation, the well treating apparatus of FIGS. 5-8 may be lowered in the well tubing 10 in the same manner as in the -modtication of FIGS. 1 4, to coat the in- 6. ternal wall with a coating material, such as, for example, a corrosion inhibitor, which also collects in the annular grooves to protect the threaded coupling and runs down vover the interior wall of the pipe sections 86. The sealing means are in the position shown in FIGS. 5 and 8 with the coil spring 98 in its compressed state and the latch members 102 in their latching position. The base of the upper sealing ring 96 closes the apertures 120, preventing the loss of the liquid in the annular space encompassed by the top and bottom sealing rings, the tubular member 92 and the well tubing 10.

As the tripping levers 114 pass the joints between pipe sections 86, the outer corners 118 are permitted to swing outward, as :shown in phantom lines in the lower part of FIG. 7, until stopped by the tripping pins 116 engaging the latch members 102. The weight of the tripping lever 114 is insuliicient to overcome the force of the Spring 98 tending to retain the latch members 102 in the groove 108.

If it is desired to dump the contents of the well treating apparatus at any particular joint, the apparatus is lowered until the 4tripping corners 11S of the tripping levers 11-4 drop into the annular groove 90 of that joint, as shown in phantom lines in the lower portion of FIG. 7. The well treating apparatus may thereupon be drawn upwardly, as indicated by the arrow. The tripping corners 118 will engage the lower end of the pipe section 86 above the groove 90, whereupon lfurther upward movement of the well treating apparatus will cause the tripping levers 114 to swing in a downward direction `about the pivots 104. Tripping pins 116 on the tripping levers 114, engaging the latch members 102, will swing the latch members downwardly out of contact with the spacer ring 100, whereupon the sealing rings 96 will be free to move downwardly Iby the -force of spring 98 to the position shown in FIG. 7 to uncover the apertures 120. The liquid in the well treating apparatus will thereupon gravitate through the apertures 120, hollow interior of the tubular member 92 and the apertures 50 in the lower end cap 44 into the bottom of the well. The same operation can take place at the bottom of the well tubing 10' in which event the tripping corners 118 engage the lower end of the well tubing and cause the tripping levers 114 to trip the latch members 102.

The axial length of the groove 90 is less than the distance between the upper and lower edges of each ring 96 at the lower end of the tubular member 92, to assure that each sealing ring 96 is at all times in sealing relation with the internal wall of the well tubing 10. f

The dimensions of the latch members 102 and the tripping levers are designed so that they may swing from the latching position in FIG. 5 to the unlatching position in FIG. 7, through the groove 90, without interference by the coupling sleeve 88.

From the foregoing, it is apparent that a novel well treating apparatus and method have been disclosed, which are eminently suitable for applying a coating to well tubing, in situ, and which apparatus may be raised or lowered without interference by any liquid or gases under pressure in the well. It will be understood that various changes may be made in the details of construction and in arrangement of the parts disclosed herein without departing from the principles of the invention and the scope of the annexed claims.

I claim:

1. A method of applying a coating to a well tubing, in situ, comprising the steps of charging a well treating apparatus with a charge of coating material having a greater aiiinity for the material of the well tubing than for the substance in the well, said charge being in excess of that required to coat the well tubing; passing the well treating apparatus through that portion of the well tubing to be treated to simultaneously displace any well fluid present and to apply the coating material to the portion of the well tubing from which well iluid has been displaced; and discharging the excess of the coating material into the well below the well tubing, whereby such excess coating material may form a reservoir to be carried along with the substance pumped from the well to further coat the well tubing and the connecting conduits.

2. A well treating apparatus for applying a corrosioninhibiting coating to the interior of a well tubing, in situ, comprising an elongated tubular member having a cross sectional area which is less than the internal cross sectional area of the well tubing, and sealing means on the opposite ends of said tubular member having an external diameter substantially the same as the internal diameter of the well tubing, providing an annular chamber between said end sealing means, tubular member and well tubing adapted to receive coating material, the portion of said tubular member between said end sealing means being imperforate and the ends of the tubular member exteriorly of said annular chamber lbeing open for the passage of tiuid therethrough when the apparatus is lowered and raised in the well tubing.

3. A well treating apparatus as recited in claim 2, including closure caps for the ends of the tubular member, said closure caps having apertures therethrough for the passage of iluid.

4. A well treating apparatus as recited in claim 2, including anges carried by and spaced from the ends of the tubular member forming abutments for the sealing means, closure caps for the ends of said tubular member, said closure caps including means to clamp the sealing means against said iianges, and apertures in said closure caps for the passage of iiuid through the well treating apparatus as said apparatus is lowered or raised through the well tubing. t

5. A well treating apparatus as recited in claim 2, 1ncluding closure caps for the ends of the tubular member, said closure caps having apertures for the passage of liuid through the treating apparatus, one of said closure caps including a head for receiving a fishing tool.

6. A well treating apparatus as recited in claim 2, 1ncluding upper and lower closure caps for the ends of the tubular member, said closure caps having apertures for the passage of well iiuid through the treating apparatus, and a driving bar within said tubular member operable to deliver a blow to the lower end cap to drive the tubular member through the well tubing, said driving bar being constructed and arranged to permit well iiuid flow through said tubular member.

7. A well treating apparatus as recited in claim 6, in which the driving bar has a cross sectional area smaller than the interior cross sectional area of said tubular member.

8. A well treating apparatus as recited in claim 6, in which the driving bar has a length shorter than the space between said end caps, remotely actuated means connected to said driving bar to reciprocate the same relative to the tubular member, and an opening through one of said end caps for the passage of said remotely actuated means.

9. A well treating apparatus as recited in claim 8, in which said opening is in the upper end cap, and is smaller than the cross sectional area of the driving bar, whereby said remotely actuated means serves the additional function of engaging the driving bar with the upper end cap for raising said well treating apparatus.

10. A well treating'apparatus as recited in claim 2, including remotely actuated means to `discharge the contents of the well treating apparatus while in a well tubing.

11. A well treating apparatus as recited in claim 10, in which said remotely actuated means comprises a valve, and means carried by said tubular member and coacting with a portion of the well tubing upon upward movement of the tubular member to actuate the valve.

12. A well treating apparatus as recited in claim 11, in which said valve comprises an opening in the tubular member controlled by the sealing means on the lower end, said sealing means being mounted for axial sliding movement on the tubular member.

13. A well treating apparatus as recited in claim 11. in which said coacting means on the tubular member for actuating the valve comprises a latch member, and a latch tripping member actuatable upon upward movement of the tubular member.

14. yA well treating apparatus as recited in claim l2, in which said coacting means for actuating the valve cornprises a latch member and a latch tripping member on the tubular member for actuating the valve and resilient means normally urging the lsealing means toward the valve opening position against restraint offered by the latch member.

15. In combination: an oil well having tubing within the boring and a lubricator above the tubing forming an extension thereof, a well treating apparatus for applying a corrosion inhibiting coating to the interior of the well tubing, in situ, said treating apparatus comprising, an elongated tubular member having a cross sectional area which is less than the internal cross sectional area of the tubing and lubricator, sealing means on the opposite ends of said tubular member having an external diameter substantially the same as the internal diameter of the tubing and lubricator providing an annular chamber between the end sealing means, tubular member and tubing or lubricator to receive and coat a protective lilm on the internal wall of the well tubing when the apparatus is lowered and raised in the tubing, said apparatus having a length not greater than the length of the lubricator to be accommodated therein, and a pair of axially spaced, valved, connections in the wall of the lubricator, adapted to register with the annular chamber between the sealing means, to permit the charging of the annular chamber with a well coating material and the venting of other material therefrom.

16. The combination as recited in claim 15, in which the upper valved connection is located in the lubricator in position to register with the extreme upper end of the annular chamber immediately below the upper sealing means of the well treating apparatus.

17. The combination as recited in claim l5, including a cable connected to the treating apparatus, 4and a pulley carried by the lubricator over which the cable passes to lower and raise the treating apparatus in the tubing and lubricator.

18. The combination as recited in claim 15, including caps on the ends of the tubular member, and apertures in said end caps for the passage of iiuid therethrough when the apparatus is raised and lowered in the tubing and lubricator.

19. The combination as recited in claim 15, including caps on the ends of the tubular member, apertures in said end caps for the passage of liuid therethrough when the apparatus is raised and lowered in the tubing and lubricator, a driving bar within said tubular member being constructed and arranged to permit the passage of fluid therethrough, the axial length of said driving bar being less than the distance between the end caps, remotely actuated means connected to said driving bar to reciprocate the same, and an opening through one of said end caps for the passage of said remotely actuated means.

20. The combination as recited in claim 19, in which the construction and arrangement to permit the passage of iiuid therethrough comprises a cross sectional area of the driving bar which is less than the internal cross sectional area of the tubular member to provide an annulus between the external surface of the driving bar and the internal surface of the tubular member.

. 2l. A method of applying a coating to a well tubing, in situ, comprising the steps of: contining in a well tube an annular charge of well coating material having an axial passageway extending therethrough; and moving said annular charge of coating material through the well apply the coating material to the portion of the well tube from which the Well fluid has thus been displaced.

References Cited in the file of this patent UNITED STATES PATENTS 2,713,908 Curtis July 26, 1955 5 2,717,038 Curtis Sept. 6, 1955 `2,954,827 Wheeler Oct.4, 1960 

1. A METHOD OF APPLYING A COATING TO A WELL TUBING, IN SITU, COMPRISING THE STEPS OF CHARGING A WELL TREATING APPARATUS WITH A CHARGE OF COATING MATERIAL HAVING A GREATER AFFINITY FOR THE MATERIAL OF THE WELL TUBING THAN FOR THE SUBSTANCE IN THE WELL, SAID CHARGE BEING IN EXCESS OF THAT REQUIRED TO COAT THE WELL TUBING; PASSING THE WELL TREATING APPARATUS THROUGH THAT PORTION OF THE WELL TUBING TO BE TREATED TO SIMULTANEOUSLY DISPLACE ANY WELL FLUID PRESENT AND TO APPLY THE COATING MATERIAL TO THE PORTION OF THE WELL TUBING FROM WHICH WELL FLUID HAS BEEN DISPLACED; AND DISCHARGING THE EXCESS OF THE COATING MATERIAL INTO THE WELL BELOW THE WELL TUBING, WHEREBY SUCH EXCESS COATING MATERIAL MAY FORM A RESERVOIR TO BE CARRIED ALONG WITH THE SUBSTANCE PUMPED FROM THE 